<div id="map"></div>
<script>
    var map = new mapboxgl.Map({
        container: 'map',
        style: 'mapbox://styles/mapbox/streets-v11',
        center: [0, 0],
        zoom: 2
    });

    var radius = 20;

    function pointOnCircle(angle) {
        return {
            'type': 'Point',
            'coordinates': [Math.cos(angle) * radius, Math.sin(angle) * radius]
        };
    }

    map.on('load', function() {
        // Add a source and layer displaying a point which will be animated in a circle.
        map.addSource('point', {
            'type': 'geojson',
            'data': pointOnCircle(0)
        });

        map.addLayer({
            'id': 'point',
            'source': 'point',
            'type': 'circle',
            'paint': {
                'circle-radius': 10,
                'circle-color': '#007cbf'
            }
        });

        function animateMarker(timestamp) {
            // Update the data to a new position based on the animation timestamp. The
            // divisor in the expression `timestamp / 1000` controls the animation speed.
            map.getSource('point').setData(pointOnCircle(timestamp / 1000));

            // Request the next frame of the animation.
            requestAnimationFrame(animateMarker);
        }

        // Start the animation.
        animateMarker(0);
    });
</script>
